<template>
  <div>
    index
    <p>{{ number }}</p>
    <button @click="plus">plus</button>
  </div>
</template>

<script>
export default {
  data() {
    return {
      number: 123,
    }
  },
  methods: {
    plus() {
      this.number += 1;
    }
  }
}
</script>